Julian Sanchez revisits Smith vs. Maryland, the Supreme Court case currently used to justify letting the government take about any data they want on your life without a warrant. Sanchez questions the logic of the case, particularly in light of sweeping technology changes since the early 70's:

Part of the problem here is that since the late '70s, we've gone a long way
toward a world in which a huge amount of our most private information is held by
third parties. A huge chunk of my e-mails from the last couple years are stored
on some server owned by Google, where ad-generating software sifts through my
private communications looking for keywords that will allow the company to
display personally-tailored advertisements for me. Now, maybe I'm naive to have
any expectation of privacy in the e-mails sitting on that server, but I do
pretty much expect that nobody at Google is actually looking through my
correspondence and passing it around to their friends. And I at leastdidn't expect until recently that some government program would be
sifting through those e-mails to see whether I used the word "jihad" some
suspicious number of times in letters to people in Saudi Arabia.

This exact same logic [used in this case] seemingly applies to any piece of data submitted
to any private third party unless the data is specifically protected
(e.g. medical records). Sorry, but this is wrong. I should be able to
have commercial transactions with third parties without the expectation
that the government can take the records for its own use without any
kind of a warrant....

The implication is that by giving a company data for use in a
transaction, we are giving them an unwritten license to do whatever
they want with the data. Do you believe you are granting this? Is it
true that you "entertain no expectation of privacy" in such
transactions? If you agree with this ability, then I assume you also
agree that the government should be able to see all your:

Credit card bills

Records of who you have emailed

Records of which Internet sites you have visited

Records of what searches you made in search engines

I also pointed out that since many people spend a lot of money to keep information private (e.g. anonymous surfing software), the market has demonstrated clearly that people, unlike the SCOTUS asserted, do have an expectation of privacy with such data.